Interrelated extracting and pulp-forming process and apparatus therefor



Feb. 9,

, R. B. ROBERTSON 1,844,600 INTERRELATED EXTRACTING AND PULP FORMINGPROCESS AND APPARATUS THEREFOR Filed April 26, 1929 /Paw raus Maer/'a/Cmozcifor "Z0 PUMP 56mm? Web 31a/vado@ 4Q tained at Patented Feb. 9,1932 UNITED STATES PATENT ori-ICE REUBEN `B. ROBERTSON, OF ASHEVILLE,NORTH CAROLINA, ASSIGNOR TO THE CHAMPION FIBRE COMPANY, OF CANTON, OHIO,A CORPORATION OF OHIO INTERRELATED EXTRACTING- AND PULP-FORMING PROCESSAND APPARATUS THEREFOR Application tiled April 26,

The present invention is concerned with a process of extracting atanning substance Irom a fibrous material containing the same, andsimultaneously preparing such material 5' in the form' of a pulpsuitable for use in making paper or the like,and with a system ofapparatus for carrying out the interre llated process. Moreparticularly, my invention finds application 1o ment of alibrousmateriaL-such for example, as the Woody parts or/and bark of oak,hemlock, Aand cl1estnut.,-containing Watersoluble constituents adaptedfor use as tanning agents, whereby the fibrous material aft-erextraction is in the condition of, and

possesses the characteristics. necessarily inherent ina Web-formingpulp.

According to the process heretofore known and used, the raw `fibrousmaterial containing Water-soluble tanning agents, in its nat.

ural, relatively'dry, condition, was first reduced by mechanical nieansto a comminuted state and the coniminuted material was extracted bybeing brought into .contact with water on the principle ofcounter-current floWgfi. e., the material was brought succes- .sively-into contact with -aqueous liquid containing less and less of thetanning agent in solution and finally with pure water.

In order to secure, in a reasonable length of time, an adequate degreeof removal of the tanning 'agents present in the fibrous material, ithas been considered necessary to bring the material to a relatively tinestate 35 of comminution. It has been the practicey to maintain theextractant at any suitable temperaturel favorable to the production ofan extract of a desired degree of purity.` In those cases where theextractant was maina temperature ator above 212 F., the extraction waseffected in pressure containers; at Working temperatures below 212 opentanks or tubs were employed.

This fine sub-'division Aof the fibrous material in its natural,relatively dry, state ref suitedl in the production of a productcontaining a large proportion off powdered material and of fibrousparticles in which the ultimate fibers and fiber 4bundles were greatlyshortened, with the result that, after extractto an extraction treat-`them. lVhen refined and 1929. Serial No. 358,352.

tion, the by-product fibrous material no lorger had value as a rawmaterial for paper pu p.

An object of the present invention is the provision of an inter-relatedtannin-extracting and paper pulp-forming process by the carrying out ofwhich a tanning substance may be extracted from a fibrous materialcontaining the same, and the said fibrous material may simultaneously beprepared in the form of a pulp suitable for use in making paper or thelike. v

My new process comprises the steps of Y partially or coarselycomminuting the raw fibrous material, subjecting the coarsely comminutedmaterial to treatment with an aqueous extractant, refining the treatedmaterial and. subjecting the same to contact with an aqueous liquid, andthickening and Washing the re-treated material. A feature of the processconsists in Washing the thickened material with an amount of watercalculated to replace. the water lost from the system in the extract andin the washed material, and the use of this Wash water in the system formaking up said losses.

The fibrous material undergoing the first extraction treatment is in astate of comminul tion suliiciently coarse-libertad to avoid materialcutting or shortening of the fibers or fiber of bundles. The refiningtreatment is effectedv upon'the material after, the fibers'and liberbundles have become softened, hence therev iining treatment tends toseparate the fibers of the bundles rather than to out or rupture 85treated in this manner, the resulting product is in a most favorablecondition for use as a paper-making pulp. In fact, a feature of. theinvention consists in effecting the thickening operation by forming therefined material into a sheet, on an appropriate thickening andsheet-forming device such as, for example, a continuous suctionthickener, on the cylinder mould of a paper machine or the like, of anyconvenient type, and washing the material with thefresh water while saidmaterial is in the sheet form. The cycli-c nature of my proce becomesapparent by tracing the water used in washing the thickened material,disregarding .the

The invention will be explained more fully by reference to theaccompanying drawing,

which is a diagrammatic representation of an operable embodiment of theprocess and of an operable system of apparatus.

In the drawing are represented, in a closed system, in addition to the'necessary piping, valves. and the like, a plurality of leach tanks 1 to12, inclusive, a refiner 13, a diffusing means 14, a web-forming device15, a pump 16. a dilute liquor storage 1T, a pump 18. and a heatingmeans 19. 2O is a coarse comminutor. rIhe leach tanks, 1 to 12,inclusive, may be either of the open, or pressure type, dependingprimarily upon whether the first extraction operation is to be effectedat below or above the boiling point. The said tanks are so arranged andso coupled by means of suitable piping, valves, and the like, asindicated, that an aqueous extractant, e. g., water, or wash water, canbe introduced into any one tank, as into leach tank 10 in theaccompanying diagram. thereafter iow continuously, as indicated, throughtanks 9, 8, etc.. and,.after passing through a plurality of the leachtanks, e. g., through tanks 10 to 3, inclusive, as indicated, bedischarged, as at tank 3, from the system and run to evaporators (notshown). The refiner 13. which may be any suitable known means forlopening up softened fiber bundles of pulpable fibrous material, in thepresence of an aqueous liquid, such as. for instance, a rod mill or arefiner of the Jordan or Claflin types, is interposed between the leachtanks 1 to 12, inclusive, and the diffuser 14 and is connected theretoby any suitable piping. The diffusing means 14 may take the form of a`tank. or series of tanks (either open or closed, as desired), which tankor tanks conveniently may be. and preferably are. provided with somesuitable means of agitation. |The purpose of the tank or tanks 14 is toprovide, in a continuously operated system, a period of contact betweenaqueous extractant and refined fibrous material sufficient toinsure'adequate extraction of tanning agents not already extracted inthe leach tanks 1 to 12, inclusive. The web-forming device 15 may be anysuitable known device for simultaneously thickening and forming a sheetor web, such, for instance, as the cylinder mould of a paper-makingmachine, or the like. The heating means 19 likewise may be any known andsuitable device for transmitting heat to a liquid.

In operation, the leach tanks will contain coarsely comminuted fibrousmaterial having progressively decreasing contents of watersolubletanning substances; in one or more of the tanks, as 11 and 12 in thediagram, there will be fibrous material which is practically exhaustedas to readily available tanning content, which material is being removedto the refiner 13 while one or more of the tanks, .as 1 and 2 in theldiagram, will be being charged with fresh coarsely comminuted fibrousmaterial; in the intermediate leach tanks will be material undergoingthe first leaching treatment with the dilute aqueous liquor from storage17, said liquor first contacting with the nearly exhausted material intank 10 and thereafter being brought successively into contact withmaterial containing progressively larger proportions of the tanningsubstances. The resulting relatively concentrated aqueous solution oftanning substances,-i. e., the extract, or strong liquor,-is withdrawnfrom the system aftcr passing through tank 3 which contains freshestmaterialfor evaporation. Then tanks 11 and 12 have been emptied of theircharge of relatively exhausted fibrous material and tanks 1 and 2 havebeen charged with fresh material, the tanks 10 and 9 are cut outI of thesystem, for discharge to the refiner 13, the aqueous extractant fromstorage 17 then being introduced into thel system of leach tanks firstat tank 8, and passing through tanks 8 to 1,inclusive, before withdrawalto evaporation.

Thel relatively exhausted fibrous material discharged from the system ofleach tanks is passed in a stream through the refiner 13 in associationwith dilute liquor from storage 17. thefiber bundles of the fibrousmaterial being opened up so as to bring the same into the condition of apulp suitable for use in making paper. The resulting stream of refinedmaterial in suspension in the liquor is then caused to pass into andthrough the diffuser 14 where the flow of pulp suspension is retarded toprovide a' period of contact between the dilute liquor and the refinedmaterial adequate to effect thorough extraction of the tanningsubstances made available in the material by the refining operation.

The pulp suspension of refined and finally exhausted fibrous materialflows from diffuser 14 to the web-forming device 15 where it isthickened in the known manner and simultaneously formed into. a sheet orweb, and is washed thereon, in the form of a sheet, with a predeterminedamount of fresh water. In the operation of thickening and washing, theweak liquor separated from the pulp is combined withl the washWater-from the Washed pulp. The amount of freshwater added is thatrequired "to replace the net amount of Water leaving the system inassociation with (1)the thickened and sheeted/pulp and (2) the extractedtanning substances in the strong 'liquor withdrawn from the system ofleach y tanks.

llOA

The Weak Wash liquor and waslf Water from thefweb-forming device 15,containing in dilute solution tanning substanceswashed out of refinedmaterial, is Withdrawn by means of pump 16 to dilute liquor storage 1i',from which it is distributed, by pump 18, to several points in thecycle. One portion of dilute liquor is returned directljv to the pulpsuspension from diffuser 14,-for diluting the same to a consistencesuitable for application to the thickener. A second portion of diluteliquor is passed through the heating means 194 and delivered in part tothe refiner 13 and in part to the system of leach tanks 1 to 12,inclusive." In case the said leach tanks areof the pressure type. aportion of the dilute liquor may by-pass the heater to the refiner; insuch a case hot liquor `from the heater is delivered tothe refiner in aquantity sufficient, when mixed with the 1 unheatedliquor, to'give theentire mass the desired temperature.

lt will be seen that the process is substantially continuous and in aclosed cycle of operations; that all ofthe tanning content 'of thefibrous material is conserved in the form of a relatively concentratedextract: that the fibrous by-product material is recovered in the formof a paper-making pulp;

. and that neither tanning substance nor fiber is discharged to waste.The process is simple; it Arequires a minimum amount of handling ofmaterial, of power and of labor. The'system of apparatus is of aneconomical character.

I claim:

1. A process for recovering water-soluble tanning substances from rawfibrous material containing the same and for simultaneously preparingsaid material inthe form of a paper web, which includes the followingsteps: (a) 'subjecting the raw fibrous material inV coarsely comminutedform to preliminary extraction with aqueous liquid obtained step o)`from step (e)- and separting the preliminai-ily extracted material fromthe resulting extractof water-[soluble tanniri'g substances: refiningthe separated material from `in the presence of aqueous liquid obtainedfrom step ('e) and subjecting it to prolonged diffusion treatment insaid liquid; (c) thickening the diffused material and simultaneouslyforming the same into a *paper web while retaining the-aqueous liquidseparated therefrom; (d) washing the web with water; and (e) combiningthe Wash Water vuid from step (-0).

A process for recovering water-soluble tanning substances from rawfibrous material containing the same and for simultaneousljv preparingsaid material in the form Yof a paper web, which includes the followingsteps: (a) subjecting the raw fibrous material in coarsel)v comminutedform to preliminary extraction with heated aqueous liquid obtained fromstep (e) and separating the preliminarilj extracted material from theresulting extract of Water-soluble tanning substances: (b) refining theseparated material from step a) in the presence of heated aqueous liquidobtained from step (e) and subjecting it to prolonged diffusiontreatment in said liquid g c) diluting the diffusion mass with aqueousliquid obtained from step (e), thickening the diffused material andsimultaneousljv forming the same into a paper web While retaining theaqueous liquid separated therefrom; (d) washing the web with Water;

and (e) combining the wash Water from step (rl) with the separatedaqueous liquid from step (c).

3. A process for recovering `Water-soluble tanning substances from rawfibrous material containing the same and for simultaneously preparingsaid material in the form of a paper Web. which includes the followingsteps:v (a) subjecting the raw fibrous material in coarselyY comminutedform to preliminary extraction with heated aqueous liquid obtainedfromstep (e) and separatingthe preliminarilv extracted material from theresulting extract of Water-soluble tanning substances; refining theseparated material from step (a) in the presence of heated aqueousliquid ob tained from step (e) and subjecting it to prolonged diffusiontreatment in said liquid; (c) diluting the diffusion mass with aqueousliquid obtained from step (e), thickening the diffused material andsimultaneously formying the same into a paper. web while retaining theaqueous liquid separated therefrom; (d) Washing the web with an amountof fresh water equalto the total water leaving the system in theWater-Wet web and in the extract obtained in step (a)'; and (e)combining the wash water from step (d) with the separatedaqueousqliquid' from step (c).

1. The process as defined in claim 1, characterized in that theextraction operation in step (a) is effected under superatmosphericpressure and at a temperature at least equal to the boiling point ofwater.

5. A system of apparatus for simultaneous- I V andcontinuously,extracting tanning substances from fibrousmaterialcontaining the same and preparing thel material in the form of a paperweb b v the process substantiallyr as described, which comprises meansfor partiallv extracting fibrous material and means for deliveringcoarsely comminuted material thereto, a refiner receiving extractedmaterial from said first named means, means for forminginto a web therefined material delivered thereto from the rener and for washing the 5web, and means for delivering liquid from said Web-forming and Washingmeans to said extraction means and to said refining means.

6. A system of apparatus for simultaneously and continuouslT extractingtanning substances from fibrous material containing the same andpreparing the material in the form of a paper web by the processsubstantially as described, which comprises means or partiallyextracting fibrous material and means for delivering coarsely comminutedfibrous material thereto, a refin'er receiving extracted material fromsaid first named means, means for forming into a web the refinedmaterial and for Washing the web, a diffuser receiving material fromsaid refiner and delivering material to said web-forming and Washingmeans, and means for delivering liquid from said Web-forming and washingmeans to said extraction means and to said refining means.

In testimonyl whereof@ afixmy signature.

REUBEN B. ROBERTSON.

